The present invention relates to a wireless headphone/ speakers sound field control circuit, which improves stereo, sound-surround sound effect, and allows the user to adjust left/right, front/back sound field contrast.
FIGS. 1 and 2 show two different wireless headphone/speakers sound field control circuits according to the prior art. In FIG. 1, wireless signal receiver 1 is connected to a signal amplifier AMP through a variable resistor VR1, and left and right speakers L SP and R SP are respectively connected to the left channel output terminal and right channel output terminal of the signal amplifier AMP. Signal from the wireless signal receiver 1 is regulated through the variable resistor VR1, then amplified through the signal amplifier AMP, and then outputted through the speakers L SP and R SP. The variable resistor VR1 is for regulating the volume. This design has drawbacks. One drawback is that it has the functions of "receiving" and "amplification", however it is not capable of processing sound field. Another drawback of this design is that the stereo effect is determined subject to the signal source, and the stereo effect of received signal well be reduced after amplification. In FIG. 2, two differential amplifiers A1 and A2 are respectively connected between the wireless signal receiver 1 and the speakers L SP and R SP, and two variable resistors VRA1 and VRA2 are respectively connected between the wireless signal receiver 1 and the differential amplifiers A1 and A2 for volume control. This design also has numerous drawbacks. One drawback of this design is that the differential amplifiers A1 and A2 simply amplify stereo signals from the wireless signal receiver 1, however they cannot reprocess received signals, i.e., the differential amplifiers A1 and A2 cannot shift the phase of main sound, background sound, and sound-surround sound of main sound and background sound. The shifting of "phase" affects the stereo effect of sound field. Further, the variable resistors VRA1 and VRA2 can only adjust volume, they cannot adjust the direction of sound field, i.e., the stereo effect, as shown in FIG. 5, is shifted between left and right, but not between multiple directions of left and right/front and back.